Foamed plastic structures



SePf- 30, 1969 G. R. HEFFNER FOAMED PLASTIC STRUCTURES -3 SheetsihoetFiled June l, 1964 INVENTOR.

Mu/m ivd/wirr Sept 30, 1969 G. R. HEFFNER 3,470,058

FOAMED PLASTIC STRUCTURES Filed June 1. 1964 5 Sheets-Sheet z;

z5 l l 'l ,25 i' n f 19 f l] INVEN OR. fw; w M 2%@ sept 30, 1969 G. R.HEFFNER 3,470,058v

FOAMED PLASTIC STRUCTURES Filed June 1, 1964 3 Sheets-Sheet L UnitedStates Patent 3,470,058 FAMED PLASTIC STRUCTURES George R. Heifner,Cincinnati, Ohio, assignor to Pullman Incorporated, Chicago, Ill., acorporation of Delaware Filed .lune 1, 1964, Ser. No. 371,426 Int. Cl.B32!) 3/12, 5/18, 3/22 U.S. Cl. 161-69 6 Claims ABSTRACT 0F THE DSCLSUREThis invention relates to structural elements formed principally ofexpanded plastic foam land more particularly the invention is directedto the formation of an insulate oor panel for use in the manufacture ofrel frigerated cargo bodies. It will be observed in the followingdescription that the invention has application Imuch wider than themanufacture of oors for refrigerated cargo bodies but its genesis was inthe solution to problems occurring in such cargo bodies and since its`advantages will be readily demonstrated in that context, the inventionwill be described in relation to refrigerated cargo bodies.

In the manufacture of refrigerated cargo bodies, the floor structure hasbeen constituted in part by spaced parallel sheets of plywood, thesheets being spaced apart by wooden cross holsters extendingtransversely to the length of the cargo body on twelve inch centers. Thecross bolsters space the sheets apart a distance of about `four inchesand are adapted to withstand the rather considerable compression forcesof a fork lift truck cornmonly used during the loading and unloading ofcargo. The space between the sheets has been filled with polyurethanefoam to impart the needed insulative quality to the floor. The uppersurface of the floor has been covered by a metallic oor structure whichtransmits the load to the insulative sandwich and additionally ispreferably designed to minimize, insofar as possible, the seepage ofliquids into the sandwich structure below.

It has been an objective of the present invention to substitute for thewooden cross holsters employed in the floor a structure which issubstantially entirely a plastic foam, preferably polyurethane. There is`much to be gained from such a substitution. The insulative qualities ofwood are markedly inferior to those of polyurethane foam. In thestructure described, the wood covers approximately twelve percent of thearea through which heat passes in the panel. If the wood could bereplaced, by a material such as foam having greater insulative quality,the insulative quality of the complete oor could be increased by tenpercent.

Still further, wood is heavy, having a weight ten times that of theplastic foam. It should be understood that for every pound of structuralweight which can be eliminated without sacrifice to the strength of theunit, a pound of pay-load can be carried by the unit.

It has been impossible within sound economic practice, to prevent theintroduction of some liquid into the sandwich panel. The cargoes,particularly the means, in the cargo bodies cause another part of theproblem. The meats drip blood onto the floor. Because of theternperature differential between the inside and outside of the cargobody, a considerable amount of moisture con- Fice denses on the metallicoor structure. The moisture cornbined with the blood causes a veryconsiderable accumulation of liquid which sloshes about and seeps itsway through the joints in the metallic floor covering and through thejoints between the panel sheets. This bloody liquid causes the wood,usually tir, in the cross bolster to rot.

In general then, about lthe only thing that can be said for wood as yastruitural element used to withstand the compressive stress of the floorpanel sandwich structure is that it is inexpensive. It is, therefore,desirable to replace as much Wood as possible in the panel.

An objective of the present invention has been to provide a structuralelement formed principally of plastic foam which can be substituted forthe wooden cross holsters to provide the support for the compressiveloading on the floor panel of the refrigerated cargo body.

The structural element of the invention is formed by first formingpolyurethane vertically in an elongated tube and after it has set,cutting the tube into short structural elements. The length of the tubeis not critical to the formation of the elements for as long as the tubeis `iilled to about one-thirtieth of its height with the liquidpolyurethane, that polyurethane will expand to fill the tube.

The ability of the foam in the tube, before it is cut, to resistcompressive stress in a direction transverse to its rise axis (verticaldirection of expansion) may vary -as much as live to one along thelength of the tube. Near the top of the tube where the iinal stages ofexpansion has taken place and the cells are quite long, the compressivestrength transverse to the rise axis is very low. The strength of thefoam parallel to the rise axis, however is great, the elongating of thecells contributing to its strength. Therefore, at the top end of thetube in which the foam has been expanded the strength parallel to therise axis is as much as four times as great as the compressive strengthperpendicular to the rise axis.

While there is some variation in the strength parallel to the rise axisalong the length of the tube, for all practical purposes the strength issubstantially uniform. At the lower portions of the tube, the elongationof the cells is not so marked and the strength attributable to theelongation of the cells is reduced, but compensating for it is thegreater density of the cells. Thus at the bottom of the tube where thereis practically no elongation of the cell structure, the foam is quitedense and has substantially the same resistance to compressive strengthin a direction parallel to the rise axis as has the structure at theupper end of the tube.

The disc elements are constituted by a tubular skin and polyurethanefoam expanded in the skin. The skin alone, of course, has minimalcompressive strength. The foam itself has minimal compressive strength,the strength being slightly greater than 40 p.s.i. parallel to the riseaxis. When the foam and skin are combined in the manner described above,the compressive strength is dramatically increased to approximately 500p.s.i. A plurality of these elements are spaced substantially uniformlythroughout the space between two panel sheets and the remaining spacebetween sheets may be filled by any insulative material including aplastic foam to form a panel element.

Another objective of the invention has been to provide a new insulatedpanel element having many applications including that of a floorstructure for refrigerated cargo bodies.

It has been another objective of the invention to provide an edgestructure for panels which is adapted for interconnecting similarlyformed panels to provide an inter-locking joint structure.

These and other objectives of the invention will become more readilyapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. l is a perspective view of a semi-trailer having a cargo body inwhich the present invention is to be used,

FIG. 2 is a fragmentary view illustrating the cargo body floor structureusing the invention,

FIGS. 3, 4, and 5 are perspective views illustrating the formation ofthe compression element of the invention,

FIG. 6 is a fragmentary perspective view showing the panel structure,

FIG. 7 is a fragmentary cross sectional view of a joint formed betweenpanel members, and

FIG. 8 is a fragmentary cross sectional view of the corner structure ofa cargo body utilizing the invention.

In its general organization and construction, the cargo body illustratedin FIG. l is well known. The known details of construction will not bedescribed specifically herein but rather attention will be particularlydirected to the manner in which the present invention is employed inmanufacture of such a cargo body.

Referring to FIG. 2, the cargo body is shown as having insulated sidewalls 10 and a floor 11 formed of insulative panels 12. The panels aremounted on steel cross bolsters 13 and the upper surface of the panelssupport a metallic iioor 14.

The floor panels are formed as a sandwich of polyurethane foam 16disposed between a bottom sheet 17 and a top sheet 18. The sheets aremaintained in their spaced parallel relation principally by discs 19 andhalf discs 20 which are the essential structural elements of the presentinvention.

The structural elements 19 and 20 which must withstand the compressionstress applied to the floor of the cargo body are formed as illustratedin FIGS. 3, 4 and 5. A hollow tube 2S which is long in comparison to itsdiameter is filled with an expanded polyurethane foam 26. By way ofexample, a kraft paper or plastic tube which is approximately fourinches in diameter and which is four feet long has about one-thirtiethof its length-about an inch and a half-filled with liquid polyurethane.T he foaming material expands and rises as it expands and formselongated cells which extend in a direction parallel to the geometricalelements forming the tubular walls. This direction of expansion and cellformation is called the foam rise axis.

The foam which is expanded in this manner exhibits anisotrophy, that is,its strength properties Vary with its diretcion of formation.Specifically, the compressive strength parallel to the foam rise axis isgreater than its compressive strength perpendicularly to the rise axis.This difference can be as great as four to one in high vertical risefoams due to extreme cell elongation during the last stage of gelformation because of the viscous drag along the side of the cavity beingfilled.

Further, disposing the foam in a tubular sheath or skin, greatlyincreases the compressive strength. The material formed, as in FIG. 3,in approximately a four inch diameter tube will support approximatelysixty-tive hundred pounds in compression, indicating that it hascompressive strength in a direction parallel to the rise axis ofapproximately 500 p.s.i.

Reference here is made specifically to polyurethane as the foamingplastic because it is presently the most commercially feasiblesubstance, but should be understood that any foam-in-place plastic iswithin the scope of the present invention.

The tube is then sliced into discs illustrated in FIG. 4, each discbeing four inches high. The precise height of the discs of course is notcritical to the invention. The four inch height is selected for theparticular trailer application wherein a block of compressive materialis required. In the embodiment described herein, the discs are used asspacers for the two sheets used to form the panels of the cargocontainer iioor.

Utilizing the discs formed as described above, insulative panels aremanufactured as illustrated in FIGS. 2 and 6. A plurality of the discsare uniformly spaced apart and sandwiched between the sheets 17 and 18which are approximately four feet by eight feet. Preferably, the discsare on twelve inch centers in the direction of the length of the cargobody as viewed in FIG. 2 and are nine inch centers in the directiontransverse to the length of the cargo body. The discs may be tacked orotherwise secured between the sheets so as to maintain the preferreduniform spacing.

The material from which the sheets are formed is not critical to theformation of the panels. The discs must be sandwiched between some formof skin to form a cavity to receive the insulative material. I prefer touse onefourth inch plywood as the skin because it is inexpensive andbecause it has a satisfactory resistance to moisture. For the purpose ofillustration, however, I have shown plywood as the bottom sheet 17 andmolded fibre glass as the top sheet, the fibre glass adhering to thepolyurethane when it is foamed in place.

Two parallel long edges of each panel have half size discs 20 disposedthereon. As shown in FIG. 2, one set of half size discs is tacked to thesheet 17 and at the opposite edge the discs 20 are tacked to the sheet18 so that when two panels are joined edge to edge, their edges may bebrought together in overlapping relation with half discs in alignment tofabricate a whole disc support.

The sandwich of sheets and discs is stood on edge with forms beingapplied around the periphery to contain the foam and to form a rabbetconfiguration along the edges having the half discs. The forms areapplied to leave a marginal strip 29 of plywood around three edges ofsheet 17. This strip facilitates attachment of the panel to the trailerframe as described below. The sandwich is then filled in the usualmanner with polyurethane foam. The resultant panel structure issubstantially entirely foam except for the outer sheets and the thintubes of paper or plastic which have been employed in the formation ofthe structural discs. The panel therefore has an improved insulativequality since the use of high heat conductivity spacers has beeneliminated. Further, the panel is adapted to carry much greatercompressive loads than a similarly formed panel which depends upon thestrength of the foam alone. Further, the strength of the panel will notvary with the random orientation of cells which is normally found in thefoam-in-place technique of panel formation.

In the manufacture of the cargo body, a frame is rst formed having aplurality of cross bolsters 13 mounted on longitudinal beams 31, thecross bolsters being on twelve inch centers. A composite rub rail 32have the H-shape illustrated in FIG. 8 is secured to the ends of thecross bolsters along the longitudinal edges of the cargo body and aroundthe forward end of the cargo body in a known manner.

The panels, starting with the forwardmost panel 34, are laid on top ofthe cross bolster and are tacked to the edges of the cross bolster as byrivets 35. The panels are preferably laid on top of the cross bolsterswith the compression discs 19 and 20 in vertical alignment with thecross bolsters 13 so that the compressive force imparted to the discswill be transmitted directly to the cross bolsters.

Succeeding panels are laid on the cross bolsters and tacked thereto withthe rabbet joints formed in overlapping relation with the half disc 20in vertical alignment. The edges of the panels at the side of the cargobody are spaced from the rub rail 32 leaving a pocket 36 extendingaround the side and front of the cargo container floor.

After the panels have been laid on the cross bolsters in the mannerdescribed, the metallic oor covering 14 may be applied. One such oorconstruction is shown in Patent No. 2,923,384.

Sheets adapted to form the side walls of the cargo container are mountedon vertical posts in a known manner. The inner of such vertical sheetsindicated at 37 in FIG. 8 overlies the pocket 36. A L-shaped member 38forms a joint between the metallic floor 14 and the vertical wall sheet37. When the vertical sheets are in place, polyurethane is introducedbetween them and foamed in place, as for example as described in mycopending application Ser. No. 251,969, led lan. 16, 1963, now U.S.Patent No. 3,229,441. The foaming polyurethane ows into intimate contactwith the side edges of the panels to form a very tight joint 39.

The tloor structure which results from the use of panels of the presentinvention has a satisfactory resistance to compressive stress, islighter than previous structures through the elimination of wood crossholsters or spacers, and has superior insulative qualities in that it isof a substantially uniform foamed polyurethane composition over itsentire area.

What is claimed is:

1. A panel for receiving transverse compressive loading comprising:

two spaced generally parallel planar sheets,

a plurality of upright spaced apart structural reinforcing spacers forsaid sheets each spacer having a tubular skin and foamable plastic oflow thermoconductivity foamed in place in said tubular skin such thatthe direction of columnar cellular growth of the foamable plastic isgenerally parallel to the side of the skin upward to the direction ofpouring, producing elongation of the cellular network in upwardgenerally parallel orientation to dene the rise axis of the foamableplastic, and said plastic foamed-in-place being in complementaryreinforcing relation with and between said tubular skin with the riseaxis of the foamable plastic generally perpendicular to planes passingthrough the cross-sectional areas of said tubular skin and generallyparallel to a plane passing through height axis of said tubular skin,

said spacers being disposed between said sheets, and spaced from oneanother, the depth of the skin and the rise axis of the plastic in thespacers being generally perpendicular to the sheets, and

plastic foamed-in-place lbetween said sheets and between said spacerswhereby the spacers in upright position are adapted to withstandIvertical compressive loading in the direction of the rise axis.

2. The invention according to claim 1, and said foamable plastic beingof polyurethane.

3. The invention according to claim 1, and said tubular skin beinggenerally circular in shape generally in the plane passing through thecross-section of the tubular skin and generally perpendicular to therise axis of the foam plastic and the axis of the tubular skin.

4. A panel construction suitable for mounting on a plurality oflongitudinally spaced transverse frame members comprising:

two spaced generally parallel planar sheets,

a plurality of upright spaced apart structural reinforcing spacers forsaid sheets each spacer having a tubular skin and foamable plastic oflow thermoconductivity foamed in place in said tubular skin such thatthe direction of columnar cellular growth of the foamable plastic isgenerally parallel to the side of the skin upward to the direction ofpouring, producing elongation of the cellular network in upwardgenerally parallel orientation to dene the rise axis of the foamableplastic, and said plastic toamed-in-place being in complementaryreinforcing relation with and between said tubular skin with the riseaxis of the foamable plastic generally perpendicular to planes passingthrough the crosssectional areas of said tubular skin and generallyparallel to a plane passing through height axis of said tubular skin,

said spacers being disposed between said sheets, and

spaced from one another, the depth of the skin and the rise axis of theplastic in the spacers being generally perpendicular to the sheets,

plastic foamed-in-place between said sheets and between said spacerswhereby the spacers in upright position are adapted to withstandvertical compressive loading in the direction of the rise axis, and

a respective spacer being adapted to be placed disposed over acomplementary transverse frame member.

5. The invention according to claim 4, and said foamable plastic beingof polyurethane.

6. The invention according to claim 4, and said tubular skin beinggenerally circular in shape generally in the plane passing through thecross section of the tubular skin and generally perpendicular to therise axis of the foam plastic and the axis of the tubular skin.

References Cited UNITED STATES PATENTS 2,923,384 2/1960 Black 52-5883,226,899 1/ 1966 Blickle 521-309 XR 2,477,852 8/1949` Bacon 161-682,744,042 5/1956 Pace 156-79 XR 2,910,730 11/1959 Risch 264-45 2,973,2952/ 1961 Rodgers 161-121 3,003,810 10/1961 Kloote et al. 161-161 XR3,231,439 l/1966 Voelker 156-79 FOREIGN PATENTS 7 7 2,18l 4/ 1957 GreatBritain.

H. F. EPSTEIN, Primary Examiner EARL M. BERGERT, Assistant Examiner U.S.Cl. X.R.

